Many photoresist strippers and residue removers have been proposed for use in the microelectronics field as downstream or back end of the manufacturing line cleaners. In the manufacturing process a thin film of photoresist is deposited on a wafer substrate, and then circuit design is imaged on the thin film. Following baking, the exposed portion of the positive resist or the unexposed portion of the negative resist is removed with a photoresist developer. The resulting image is then transferred to the underlying material, which is generally a dielectric or metal, by way of reactive plasma etch gases or chemical etchant solutions. The etchant gases or chemical etchant solutions selectively attack the photoresist-unprotected area of the substrate. As a result of the plasma etching process, photoresist, etching gas and etched material by-products are deposited as residues around or on the sidewall of the etched openings on the substrate.
Additionally, following termination of the etching step, the resist mask must be removed from the protected area of the wafer so that the final finishing operation can take place. This can be accomplished in a plasma ashing step by the use of suitable plasma ashing gases or wet chemical strippers. Finding a suitable cleaning composition for removal of this resist mask material without adversely affecting, e.g., corroding, dissolving or dulling, the metal circuitry has also proven problematic.
As microelectronic fabrication integration levels have increased and patterned nanoelectronic and microelectronic device dimensions have decreased for the production of current and future generation nanoelectronic and microelectronic semiconductor devices and other items such as flat panel displays, it has become increasingly common in the art to employ copper metallizations, low-κ (both porous and non-porous) and high-κ dielectrics. These materials have presented additional challenges to find acceptable cleaner compositions. Many process technology compositions that have been previously developed for “traditional” or “conventional” semiconductor devices containing Al/SiO2, Al(Cu)/SiO2, or Al/Mo/SiO2 structures cannot be employed with copper, tungsten, tantalum, nickel, gold, cobalt, palladium, platinum, chromium, ruthenium, rhodium, iridium, hafnium, titanium, molybdenum, tin and other metallized, and low-κ or high-κ dielectric structures. For example, hydroxylamine based stripper or residue remover compositions are successfully used for cleaning devices with Al metallizations, but are practically unsuitable for those with copper and other metallizations. Similarly, many copper metallized/low-κ strippers are not suitable for Al metallized devices unless significant adjustments in the compositions are made.
Removal of these etch and/or ash residues following the plasma etch and/or ashing process has proved problematic. Failure to completely remove or neutralize these residues can result in the absorption of moisture and the formation of undesirable materials that can cause corrosion to the metal structures or electrical defects to the integrated circuitry. The circuitry materials are corroded by the undesirable materials and produce discontinuances in the circuitry wiring and undesirable increases in electrical resistance. This problem is also especially evident in removing sidewall deposited photoresist or residues and surface-hardened photoresist hardened due to UV radiation, reactive ion etching or ion implantation processes. There is also a problem of removing photoresist and is other residues when they are present in structures having high aspect ratio openings, including difficult submicron grooves and narrow crevices.
The current back end cleaners show a wide range of compatibility with certain, sensitive dielectrics and metallizations, ranging from totally unacceptable to marginally satisfactory. Many of the current strippers or residue cleaners are not acceptable for advanced interconnect materials such as porous and low-κ dielectrics and copper metallizations. Additionally, the typical alkaline cleaning solutions employed are overly aggressive towards porous and low-κ and high-κ dielectrics and/or copper metallizations. Moreover, many of these alkaline cleaning compositions contain organic solvents that show poor product stability, especially at higher pH ranges and at higher process temperatures.
In an attempt to at least partially address these problems, it has been proposed to employ supercritical fluids to remove such organic and inorganic residues from such substrates. Examples of such proposals are found in the disclosure in U.S. Pat. Nos. 6,242,165B1, 6,306,564B1, 6,500,605B1 and 6,653,236B2. In these patents it is proposed to clean substrates with supercritical fluids such as carbon dioxide, ammonia, nitrous oxide, carbon monoxide, and inert gases such as nitrogen, helium, neon, argon, krypton and xenon, and particularly carbon dioxide. It is proposed to employ supercritical fluids alone or with various simple modifiers, such as oxidizers (U.S. Pat. No. 6,242,265B1), carbon dioxide with chemical solvents (U.S. Pat. No. 6,306,564B1), and carbon dioxide, an amine and a solvent (U.S. Pat. No. 6,500,605B1). However, the cleaning efficiencies and capabilities of the supercritical fluids alone or with the simple modifiers have been limited in removing bulk photoresist and difficult-to-remove plasma generated residues.